As is well known components if gas turbine engines exposed to hot gases of combustion cannot stand prolonged exposure to unusually high operating temperatures or else they suffer premature failure due to thermal fatigue, thermal stresses and the like. While the upper temperature limit to which such components may be exposed can be increased by resort to exotic materials, this solution is not popular because of the increased cost associated therewith.
Consequently, most efforts directed towards preventing exposure of such components to undesirably high temperatures have fallen in one or both of two general categories. Those categories include the addition of so-called dilution air to the hot gases of combustion before they are applied to the turbine nozzle and turbine wheel. The dilution air brings down the temperature of the hot gases of combustion to a value at which the turbine components can readily operate. To be effective, this solution requires good mixing of the dilution air with the hot gases of combustion or else hot spots will exist; and such hot spots and the resulting temperature gradients induce thermal stresses.
Another approach to solving the problem involves the cooling of the components that are exposed to the hot gases of combustion so that they themselves do not operate at excessive temperatures.
One component of a turbine engine requiring protection from hot gases of combustion is the turbine nozzle. The nozzle has which receive the hot gases of combustion from the turbine engine combustor and directs the same against the blades on a turbine wheel to drive the same. Typically, dilution air is introduced into the following stream of gases upstream of the turbine nozzle and, not infrequently, some provision is made for flowing cooling air, usually taken from the compressor of the engine, through the individual vanes or blades making up the turbine nozzle to provide both convective and conductive cooling of the vanes. In the typical case, the vanes are provided with outlet openings on their respective surfaces either simply to allow the flow of cooling air to exit into the gas stream, or in many cases, to provide film air cooling on the exterior of the vanes. The holes or apertures used are typically quite small and the formation of the same is costly. Nonetheless, cooling of nozzle vanes by flowing air through the interior thereof for cooling purposes has proven to be effective.
The present invention is directed to providing a less costly, yet highly effective, means of promoting the cooling of nozzle vanes in a gas turbine engine.